1. Field of the Invention
The present invention relates to an improved insulating material; the insulating material being a mixture of an insulating fluid and solid bodies.
2. Description of the Related Art
Various devices utilize gas-filled vessels such as interrupting units at high voltage. It is often required to actuate parts within the vessel by employing a ground-potential mechanism and an insulating actuating member that connects the ground potential mechanism to the parts within the vessel.
The actuating member often passes through a hollow insulating support column that is filled with the same gas as the vessel at top where the gas is able to communicate between the vessel and the support column. This arrangement includes the drawbacks that the support column has a number of joints that must be sealed against gas leakage. This requires special handling during manufacture. Field assembly is also complicated since gas is normally added at the time of installation and contamination must be avoided either as to the pressurized vessel or the support column. Additionally, while in service, the gas presure must be monitored by special monitoring equipment to ensure that no breach of insulating integrity has occurred in the column and the interrupting unit.
An insulating liquid can be used to overcome the drawbacks with pressurized gas columns. The liquid is easier to seal and contamination is more easily avoided. However, a desirable fluid is relatively expensive and if the fluid is lost through leakage, moisture can enter the column and collect on the internal surfaces thereof; the insulating properties of the column thereby being reduced.
A solid insulation can be utilized but it is difficult to provide movement of actuating members through solid insultion. Further, it is difficult to prevent air pockets that would lead to dielectric breakdown.
Prior arrangement have utilized an insulating fluid and sand where the sand settles to the bottom and packs densely or cakes. Movement of an actuating member through such an arrangement would also prove difficult due to the high viscous drag on the actuating member and the settling and packing of the sand.
While these arrangements are generally suitable for some purposes, it is always desirable to provide improved insulating materials and insulating opertor columns that exhibit fewer shortcomings in the areas of sealing problems, maintenance, thermal expansion problems, air pockets and uniformity.